What is shelterbelt renovation? USDA Natural Resources Conservation Service defines it as the widening, partial replanting, removal and replacement of selected trees and shrubs or other steps taken to improve and existing shelterbelt. It involves inventory, evaluation and improvement of the health of trees and shrubs and the overall function of shelterbelts through the use one or more of the following silvicultural techniques.
Release of Sod-bound Trees and/or Shrubs - Release from sod may be accomplished with tillage or use of herbicides. Disc cultivators throw soil one direction which will create hollowed out areas between tree rows and may harm the tree's vital feeder roots. Also, tillage should never be deeper than three inches to protect feeder roots. Many types of chemicals exist, but they all fit into two basic categories: pre-emergence and post- emergence. The most common pre-emergence are Princep (Simazine) and Casaron (Dichlobenil) and the most common post-emergence is Round-up (Glyphosate).
Underplanting or Interplanting - In this practice trees or shrubs are planted within an existing windbreak without tree removal. They are planted in rows between existing rows or between trees in an existing row. Overtopped plants even though they are shade tolerant, will grow slowly and will develop poor form and spindly growth. Cedar and Juniper are the most widely used species. Other shade tolerant species are hackberry, chokecherry, bur oak and boxelder.
Row Removal and Replacement - Dead or dying rows are removed and replaced within the existing windbreak. It can be done to beef up any or all levels of the windbreak. After tree removal the site should be fallowed one year. Where multiple adjacent rows are removed, it may be beneficial to plant one less row than what was removed.
Supplemental Planting & Expansion - Additional land is needed for expansion and there needs to be room for it. One of the main benefits is that tree removal is not necessary. If the windbreak is in the correct place and correctly positioned, make sure that added rows do not negatively affect wind and snow drift patterns relative to the area to be protected.
Thinning, Pruning and Coppicing - Release thinning is used to release adjacent trees or rows by removing selected trees, partial row or entire rows. Pruning has limited use in windbreak renovation. It is sometimes used to remove diseased branches for sanitation. Coppicing is used to rejuvenate shrubs or even hardwood trees that have sprouting capabilities. It can even be used on hardwood trees less than 12 inches in diameter and under 20 years of age. Almost any shrub species can be rejuvenated through coppicing. Broadleaf trees that have shown good results are green ash, cottonwood, Russian olive, boxelder and the elms, especially Siberian elm. Cut back 6 to 8 inches above the ground to provide a good shrub row.
Managing Reproduction - In many older multiple row windbreaks that have been protected from livestock, natural reproduction of existing species will occur. A couple methods have been suggested to utilize this new growth. Leave the regeneration until it is about 8 to 10 years old then begin some selective cutting. The thinning of the regeneration can be done in rows to conform to the original windbreak design or it can be managed similar to a natural forest.
My source for this news release was South Dakota Department of Agriculture, Division of Resource Conservation and Forestry. If you would like more information about Shelterbelt Renovation, contact Bob Drown at the Conservation Office at 605-244-5222, Extension 4 or by e-mail at email@example.com.